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Schedule your energy, not your hours

9 min read

For knowledge work, energy management means planning the day around when your mind works best, instead of treating every hour on the calendar as equal. It takes 3 steps: for a few days, write one word for each hour you work (sharp, okay or fog); then put the work that needs thinking and deciding in the sharp hours and the routine work in the fog; then protect the sharp window the way you’d protect an important meeting.

The research behind this is real and modest. People differ a lot in when their body clock runs, and in lab studies many do better on attention-heavy tasks at their own peak time of day. One study even found that insight puzzles went better at people’s off-peak hour. None of it can tell you which of your hours are which. A few days of notes can.

The idea has a wider use. Tony Schwartz and Catherine McCarthy’s Harvard Business Review article “Manage Your Energy, Not Your Time” (2007) points it at something bigger: the burnout that follows when people meet rising demands with longer and longer hours. This post takes the narrow version: the hours of one working day, and which work goes in which.

8 identical boxes

Open a calendar and a working day is 8 boxes of equal height, 9 to 5. The grid is accurate about time. It says nothing about you.

You already know your 10am and your 3pm are different people. One of them can hold a whole argument in their head and spot the flaw in paragraph four. The other can rename files. Ordinary planning asks only how long a task will take, then finds a gap that size. A 2-hour draft fits as neatly into 2pm to 4pm as into 9 to 11, and on the screen nobody can see the difference. You can, by about 2.40pm.

Scheduling by energy keeps the boxes. It changes what you let into them.

Chronotype and productivity: what the research says

People run on different clocks

In 2003, Till Roenneberg, Anna Wirz-Justice and Martha Merrow reported a pilot study of 500 completed questionnaires asking people when they sleep on workdays and on free days, how much daylight they get and which type they think they are. The paper’s abstract opens: “Human behavior shows large interindividual variation in temporal organization. Extreme ‘larks’ wake up when extreme ‘owls’ fall asleep.”

They also found that late types build up a considerable sleep debt over the working week and make it up on free days by sleeping several hours longer. The timing wasn’t fixed at birth, either: people who spent more time outdoors in daylight slept earlier.

The paper is about sleep. It says nothing about when anyone writes well. What it gives you is the premise: one office’s 9 to 5 lands at very different points on very different internal clocks.

The synchrony effect

The idea that you do better at your own peak has a name, the synchrony effect, and the early work on it was about memory and age. In 1993, Cynthia May, Lynn Hasher and Ellen Stoltzfus found, using a standard questionnaire, that most younger adults were evening or neutral types and the vast majority of older adults were morning types. Then they tested both groups’ recognition memory in the morning or in the late afternoon. In the late afternoon, when the younger adults were at their best, the age differences were substantial. In the morning, when the older adults were at their peak, there were none. The authors concluded that “synchrony between optimal performance periods and the time at which testing is conducted may well be a critical variable” in group differences.

That paper is about age differences in memory, and it gets cited for more than it tested. Later work widened it. May and Hasher (1998) found that inhibitory control, the ability to set aside thoughts that are no longer relevant and hold back a strong response you don’t want, was greatest at people’s optimal times, in younger and older adults alike. Access to well-learned responses wasn’t affected by the time of testing. A 2007 review by Christina Schmidt and colleagues found time-of-day effects across tasks measuring attention, executive functioning and memory, depending on chronotype and especially on how well a person’s peak lines up with the hour of testing.

What these studies don’t show

None of them followed anyone through a working week. They are short lab tasks, such as recognition tests and the Stroop test. The fair summary is modest: on tasks that lean on controlling your attention, many people do measurably better near their own peak than away from it. Nothing in that says your peak is 9am, or that your Monday matches your Friday. Finding your hours is the part you do yourself.

Step 1: notice, one word per hour

For your next 3 to 5 working days, keep a strip of paper by the keyboard. At the end of each hour you work, write the hour and one word.

  • Sharp: you can hold a hard problem in your head, and you don’t drift.
  • Okay: real work gets done, with a few trips to the inbox.
  • Fog: you read the same sentence twice, then check your phone.

That’s the whole method. Don’t score yourself out of 10, and don’t analyse anything until the days are done. The scale is coarse on purpose: you’re looking for the shape of a day, and a finer one mostly measures how you feel about scoring.

A Tuesday might come out like this:

09  sharp
10  sharp
11  okay
12  okay
13  fog
14  fog
15  okay
16  okay

One day is noise; a bad night or a tense meeting will flatten any hour. Look for a run of sharp hours that keeps turning up in roughly the same place. If it wanders, note what else happened that day, because the pattern may be about sleep or meetings more than the clock. If you’re a late type, expect it later than the office does. The case against forcing an early start has its own post.

Step 2: match the work to the hour

The best time of day for deep work is your sharp window, wherever your notes put it. Sort the rest by the kind of attention each task needs, not by how long it takes.

  • Sharp hours, for creating and deciding. The first draft of the proposal. The budget, if the budget means choices. The bug nobody has found. The decision you’ve been carrying around for a week. Work where one wrong turn costs you the next hour.
  • Okay hours, for working with what exists. Editing, reviews, most meetings, calls, the steady middle of a project.
  • Fog hours, for the routine. Email that needs a one-line reply, expenses, bookings, filing, the form from the bank, errands.

The lab work gives this a rough logic. What suffered off-peak was control: ignoring what doesn’t matter, holding back the obvious wrong answer. Well-learned responses held up all day, and a lot of admin is well-learned. You know how to do it; it just has to get done.

Say your notes show sharp from 9 to 11, fog straight after lunch and okay either side. Tuesday then looks like this: the budget proposal from 9 to 11, with email shut. The team meeting you can’t move at 11. Expenses, the dentist and the 6 emails that need one line at 2. Edits and calls from 3 to 5. The same 8 hours as before, and the hard thing got the good ones. An owl’s Tuesday runs the other way round: replies and admin first, the proposal at 4.

Spending a sharp hour on expense receipts is the most expensive admin you will ever do.

If you plan the day in 3 lines, this is where they land. The one that matters goes in the sharp window, and the quick one goes in the fog.

Step 3: protect the sharp window

Treat the sharp window like a meeting with someone important. It is one.

  • Put it in the calendar under the work’s name. “Budget draft” is harder to give away than “Focus time”, for you and for anyone booking over it.
  • Offer okay hours for meetings. Most meetings don’t need your best thinking. They need you there and awake.
  • Keep email shut at the start of the window. Email is fog work with a talent for looking urgent.
  • Protect some days if you can’t protect all of them. A sharp window you keep on Tuesdays and Thursdays beats a daily one you keep losing.

The fair objection is that your calendar isn’t yours. A manager books the mornings, a small child books the evenings, a shift rota books everything. Then the method shrinks; it doesn’t break. Find the one sharp hour you do control, even if it comes once a week, and give it to the hard thing. When you can’t move the meeting, move the preparation for it into the sharp hour, and let the meeting land where it lands.

When to do creative work: what fog is good for

Fog hours aren’t wasted. Most of them should go to the routine, the inbox and the errands, and every errand done in the fog is one that isn’t eating a sharp hour.

There’s a second use, and it’s the oddest result in this area. In 2011, Mareike Wieth and Rose Zacks sorted 428 undergraduates into morning, evening and neutral types by questionnaire: 195 came out as evening types and just 28 as morning types. Each student tried 6 problems, 4 minutes apiece. Half were analytic, the kind you work through step by step. Half were insight problems, the kind where you’re stuck until suddenly you aren’t: a prisoner escapes a tower with a rope half as long as the drop, by dividing it in half and tying the two ends together. How? Half the students were tested between 8.30 and 9.30am, half between 4 and 5.30pm.

On all 3 insight problems, students tested at their off-peak time did better: 56, 22 and 49 per cent solved them, against 51, 16 and 31 per cent at their peak. The analytic problems showed no consistent time-of-day effect. With far more owls than larks in the sample, a plain morning advantage could have explained it, but the neutral students did no better on insight problems in the morning than in the afternoon. The mismatch seems to be what helped.

The authors’ explanation is the filter from the synchrony studies: off-peak, inhibitory control is weaker. On a problem where the obvious path is the wrong one, a leakier filter can let in the stray idea that turns out to be right. Their conclusion is careful: tasks involving creativity “might benefit from a non-optimal time of day.”

It’s one study, of students, on 4-minute puzzles, and a riddle is a long way from a product plan. So don’t move your creative work into your worst hour. Do something smaller. When you’re stuck on a problem that needs a new angle rather than more effort, take it into a fog hour and look at it loosely. Walk with it, or sketch it badly. If nothing comes, you’ve lost an hour you were going to spend on receipts. If something does, write it down and test it in tomorrow’s sharp window, because the filter that let the good idea in lets bad ones in too.

(The prisoner cut the rope lengthwise.)

Start tomorrow

Write the hours you work down the edge of a page and leave a space beside each one. That’s all the equipment. At the end of the week, read the words back as part of your weekly review, find your sharp run, and move one hard thing into it.

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